Process of refining fatty acids



Patented on. 29, 1940 UNITED STATES PROCESS OFBEFINING FATTY ACIDS Arthur W. Hixson, Leonia, N. J., and Ralph Miller, New York, N. Y., asslgnors to The Chemical Foundation, Incorporated, a corporation of Delaware No Drawing. Application October 19, 1939, Serial No. 300,208

9 Claims. (or. 260-419) This invention is concerned with the refining of fatty acids. The universal method of refining crude fatty acids is by distillation. The two principal objections to this method are that it is costly to practice andthe yields are relatively low. We have discovered that crude-fatty acids can be inexpensively refined with practically 100 per cent. yields by the use of liquefied, normally gaseous hydrocarbons.

Our unique process of refining crude fatty acids consists, in part, of dissolving crude fatty acids under, pressure in several volumes of a liquefied, normally gaseous hydrocarbon. We havefound that fattyacids such as stearic, oleic, palmitic, linoleic, etc., are completely soluble at room temperature in liquefied, normally gaseous hydrocarbons such as propane, ethane and butane. The resinous, tarry materials also present in crude fatty acids are only slightly soluble in liquefied, normally gaseous hydrocarbons. An effective preliminary separation is achieved by dissolving the fatty acids present in the crude fatty acids in a hydrocarbon such as propane, separating the clear solution from the insoluble 5 residue, and then separating the hydrocarbon from the fatty acid. There is an enormous difference in vapor pressure between normally gaseous hydrocarbons and fatty acids, so that the hydrocarbons can be very easily separated by distillation. The result of this procedure is an impure product but one that is considerably purer than the initial material. Y

The clear solution mentioned above is reddishbrown in color, indicating the presence of some colored impurities. We have found that if this clear solution is heated under pressure, a second liquid phase appears. In general, it is found that if the temperature is raised to the point where a second liquid phase begins to form and the temperature then-maintained at that point for a reasonable amount of time, a lower layer composed of the second liquid phase will form. The

lower layer-mill here a lame ,tqtal color present'concentra'ted iiiit. in ads desired, the lower layer may be separated from the upper'layer at this time. The lower layer is comliquid phase after each rise in temperature, a

multiplicity of fractions may be secured. It has been found that the fractions obtained at the lower temperatures resemble the insoluble residue. Those fractions secured at higher tem- 5 peratures resemble the fatty acids. The principal impurities in crude fatty acids are the tarry materials whose structure is so complex that they are dismissed under the broad'term of resinous materials and unsplit triglycerides. The fractions obtained at lower temperatures are resinous materials while those obtained at higher temperatures resemble the original fats.

To insure economical working of the process it is necessary to remove and recover the hydrocarbon associated with each fraction. If the temperature is raised sufliciently high, the fatty acids will precipitate. If heating is stopped just prior to the temperature at which the fatty acids will precipitate, upon examination, the hydrocarbon solution will be found to be colorless. At this point the hydrocarbon. may be separated from the fatty acid in suitable distillation equipment. Water-white fatty acids are the final product. 25

It has been mentioned above that the lower layerscontain a small quantity of fatty acids. Whenthe impurities precipitate, they dissolve an appreciable amount of the hydrocarbon solvent. The fatty acids present are soluble in this second liquid phase. For this reason, the fatty acid is distributed between the hydrocarbon solution and the second liquid phase. To recover the fatty acid in the second liquid phase, it is only necessary to treat the separated second liquid phase with several additional volumes of the liquefied normally gaseous hydrocarbon at suitable temperatures. The most eflicient method of recovering the fatty acid present in the second or lower liquid phase is to employ a continuous counter-current process. A continuous counter-current process permits yields approaching 100 per cent. instead centasecured. by distillation.

'of the equipment is equal to the volume of the 50 solution, fatty acids start to precipitate as a second liquidphase in the neigh-borhood of C. The composition of the hydrocarbon solvent, the ratio of volume of hydrocarbon to volume of fatty acid, the type of impurities present, and the u ratio of vapor space to liquid volume of the equipment, are all important variables. Various costs such as raw material, labor, steam, electricity, hydrocarbon solvent. maintenance, and the selling price of the finished product, all dictate the most economical method of employing this invention.

Having thus described our invention, we claim: i

1. The process of separating fatty acids from tar-like, resinous materials consisting in dissolving the acids in a liquefied, normally gaseous hy-'- drocarbon in which the said materials are substantially insoluble, separating the hydrocarbon solution from the said materials and separating the normally gaseous hydrocarbon from the fatty acids.

2. The process of separating fatty acids from tar-like, resinous materials with which they are commingled, consisting in dissolving the acids in propane, separating the propane solution from the said materials and distilling said solution to recover the fatty acids and propane separately.

3. In a process for refining fatty acids, the step of dissolving the fatty acids in a liquefied, normally gaseous hydrocarbon.

4. In a process for.refinin'g i'atty acids, the step of dissolving the fatty acids in a mixture of liquefied, normally gaseous hydrocarbons.

5. In a process for refining fatty acids, the step of dissolving the fatty acids in liquid propane.

6. The process of refining crude fatty acids consisting in dissolving the acids in a liquefied, normally gaseous hydrocarbon; separating the hydrocarbon solution" from any insoluble residue; heating the solution under pressure to precipitate the dissolved impurities as a second liquid phase; separating the second liquid phase from the hydrocarbon solution; and recovering a pure fatty acid from the hydrocarbon solution by removing the hydrocarbon.

7. The process of refining crude fatty acids consisting in dissolving the acids in liquid propane; separating the propane solution from any insoluble residue; heating the propane solution under pressure to precipitate the dissolved impurities, as a second phase; separating the second liquid phase from the propane solution; and recovering the purified fatty acids from the propane solution by distilling the solution to recover pure propane and pure fatty acids.

8. The process of refining crude fatty acids consisting in dissolving the acids in a mixture of liquefied, normally gaseous hydrocarbons;

heating the resulting solution under pressure until the dissolved impurities start to precipitate as a second liquid phase; maintaining the temperature at that point until a lowerlayer composed of the second liquid phase has formed; separating the lower layer from the hydrocarbon solution; heating the hydrocarbon solution to a slightly higher temperature to cause an additional quantity of impurities to precipitate and again form a lower layer; separating such new lower layer from the hydrocarbon solution and continuing the process until the hydrocarbon solution is free from impurities; and removing the hydrocarbon contained in each fraction into which the original solution has thus been successively divided.

9. The process of refining crude fatty acids consisting in dissolving the acids in liquid propane; heating the propane solution under pressure until 'the dissolved impurities start to precipitate as a second liquid phase; maintaining the temperature at that point until a lower liquid layer composed of the second liquid phase has formed; separating the lower layer from the propane solution; heating the propane solution to a slightly higher temperature to cause an additional quantity of impurities to precipitate and thereby to form a lower layer once more; separating such second lower layer from the propane solution and continuing the process until the propane solution is free from impurities; and removing the propane contained in each fraction into which the original solution has been divided.

ARTHUR W. HIXSON. RALPH MILLER. 

